diff --git a/src/middlewared/middlewared/plugins/disk_/wipe.py b/src/middlewared/middlewared/plugins/disk_/wipe.py
index 0bd8a3a3d3b1b..e5a656599fe8a 100644
--- a/src/middlewared/middlewared/plugins/disk_/wipe.py
+++ b/src/middlewared/middlewared/plugins/disk_/wipe.py
@@ -75,7 +75,7 @@ def _wipe_impl(self, job, dev, mode, event):
             # no reason to write more than 1MB at a time
             # or kernel will break them into smaller chunks
             if mode in ('QUICK', 'FULL'):
-                to_write = b'0' * CHUNK
+                to_write = b'\0' * CHUNK
             else:
                 to_write = os.urandom(CHUNK)
 
diff --git a/src/middlewared/middlewared/plugins/pool_/expand.py b/src/middlewared/middlewared/plugins/pool_/expand.py
index ea3d0f234a69c..4b0feb4149c05 100644
--- a/src/middlewared/middlewared/plugins/pool_/expand.py
+++ b/src/middlewared/middlewared/plugins/pool_/expand.py
@@ -85,7 +85,7 @@ async def expand_partition(self, part_data):
         def wipe_label():
             with open(os.path.join('/dev', part_data['disk']), 'r+b') as f:
                 f.seek(wipe_start)
-                f.write(b'0' * wipe_size)
+                f.write(b'\0' * wipe_size)
 
         await self.middleware.run_in_thread(wipe_label)